Ali Larijani challenged an opposition politician to "present evidence of such outrages" about detainee abuse.

Ali Larijani said that a special panel of Iran's parliament, or Majlis, conducted a "precise and comprehensive inquiry" into the treatment at Tehran's Evin and Kahrizak prisons, and found "no cases of rape or sexual abuse," Press TV reported.

Larijani's fiery response was to accusations made by opposition candidate Mehdi Karrubi who, along with opposition leader Mir Hossein Moussavi, ran against hardline President Mahmoud Ahmadinejad in the June 12 election. Iran's election authority declared Ahmadinejad the overwhelming winner of the race, sparking hundreds of thousands of Iranians to take to the streets in protests.

A brutal government crackdown followed, leading to the arrests of more than 1,000 people. The official death toll from the post-election unrest is 30, though opposition leaders say it's more than twice that figure, Press TV reported.

In an open letter to Ali Akbar Hashemi Rafsanjani posted Saturday on his party's Web site, reformist Mehdi Karrubi says an "impartial committee" is needed to "investigate these tragedies with transparency until they are resolved." He said he is willing to lead the investigation in a "truthful, unbiased fashion."

"Some of the former detainees have told of such brutal and violent, repeated rapes of the young women [in detention] that have caused irreparable damage to their reproductive systems," Karrubi says in the letter. "Others have raped our detained young men with such brutality that they [the victims] have been afflicted by depression and are no longer speaking with anyone and refuse to leave the dark corners of their houses."

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The treatment of detainees at Iran's prisons has increasingly become a divisive issue within Iran's Islamic leadership, as reformists continue to accuse the hardline government of allowing of abuse and torture in attempts to coerce false confessions.

Opposition figures such as Karrubi have compared the treatment of detainees now to political prisoners abused under the "oppressing regime" of the Shah of Iran, who was overthrown by the Islamic Revolution in 1979.

"I don't think that in the 15 years, leading up to the victory of the revolution, individuals from the communists, armed resistance, liberation front and the Islamic party -- who were all imprisoned and living together in prison -- had ever heard of or seen such things," Karrubi said.

Larijani on Wednesday challenged Karrubi to "present evidence of such outrages" for the Majlis to investigate, according to Press TV.

Iranian media has reported that Ayatollah Ali Khamenei, Iran's supreme leader, has ordered one prison, Kahrizak, shut down amid reports it did not measure up to the required standards. Kahrizak's chief was fired and arrested over allegations of detainee mistreatment, according to local reports Saturday.

A special parliamentary committee has made rounds at Tehran's Evin prison, but did not find any signs of abuse, according to recent media reports. Hundreds of detainees have since been reportedly released from Evin, though "political figures" were held and put on trial.

A spokesman for Iran's Foreign Ministry Monday denied that prisoners had been tortured.

"What kind of talk is this? There was never any pressure used against these people," Hassan Qashqavi said, according to the semi-official Mehr news agency.